1. Field of the Invention
The present invention relates to shoulder prostheses. More particularly, the present invention relates to a modular shoulder prosthesis system including connectors which allow standard prosthesis stems and heads to be interconnected in various configurations.
2. Description of the Prior Art
Early shoulder prostheses directly mimicked the upper portion of the humerus which they were designed to replace. That is, they were typically unitary structures including a stem, to be implanted within the humerus, and a head, to be positioned within the glenoid cavity of the scapula.
One problem with conventional unitary shoulder prostheses was the necessity of maintaining large inventories of differently configured prostheses to accommodate patients'differing anatomies. Not only were prostheses with different sizes of heads and stems required, but also prostheses with the head and stem configured at various tilt angles and radial offsets relative to one another. These various configurations were required in each size category.
To reduce the required inventory, assorted modular prostheses have been devised. Prior art modular systems have generally been designed to allow flexibility with respect to either the tilt angle or the radial offset between the head and stem. Although some of these prior art modular systems utilize either a "standard" head or a "standard" stem, most still require a plurality of either the heads or the stems to provide complete tilt angle and radial offset flexibility. None of the prior art systems provides complete tilt angle and radial offset flexibility without requiring different modular head or stem components of each given size. As a result, substantial inventories of either the stems or heads, which are the most expensive components, have had to be maintained.
Accordingly, there is a need for a modular shoulder prosthesis system which allows virtually complete flexibility of both tilt angle and radial offset adjustment while utilizing standard heads and stems.